Pack 21 - Gene Expression Flashcards
how is transcription regulated?
transcriptional factors
how is gene transcription stimulated?
each transcriptional factor has a site that binds to a specific base sequence of the DNA - promoter region
when the transcriptional factor and the promoter region bind it allows RNA polymerase to bind and transcription begins
how does oestrogen affect gene transcription?
oestrogen is a lipid so it crosses the cell membrane by lipid diffusion and enters the cytoplasm
oestrogen binds to the receptor site on the transcription factor and changes its shape
results in the inhibitor molecule no longer fitting into the transcription factor so it detaches, exposing the DNA binding site
the active transcription factor diffuses into the nucleus
nucleus and transcription factor binds to a specific base sequence on a DNA promoter region upstream of RNA polymerase
binding stimulates RNA polymerase to transcribe genes and so stimulates protein synthesis
what does RNAi do to gene expression?
moves into the cytoplasm and becomes single stranded
it binds to specific mRNA molecules with a complementary base sequence by complementary base pairing
cuts mRNA in two
mRNA can no longer be translated so protein synthesis stops
what are the four types of stem cells?
totipotent cells - any type of body cell
pluripotent - any type of cell
multipotent - only found in mature animals - limited number of of different cell type
unipotent - only found in mature animals - only one type of cell
what is the difference between pluripotent and Unipotent?
pluripotent cells can differentiate into all cells of the adult body
unipotent cells can differentiate into only one cell
what is epigentics?
heritable changes in gene function without changes to the base sequence of DNA
what does it mean when the gene is coiled up?
hard to read DNA
genes are switched off
what does it mean when the gene is loose?
easy to read
genes are switched on
transcription factor can access the gene so mRNA transcribed
what is the acetylation/deacetylation of histones?
causes the positive charge between the histones to disappear and the genes become less tightly packed
causes the positive charge to become stronger and the histones attract and coil together more
what is methylation?
addition of a methyl group (CH3) to a molecule
increased prevents transcription factors binding to the DNA
how can transcription inhibited?
increased methylation
decreased acetylation
what is a benign tumour?
mass of cells that hasn’t spread to neighbouring tissues
not cancerous
potential to turn cancerous
what is a malignant tumour?
uncontrollably dividing cell groups that might spread (metastasise)
cancerous
what do proto - oncogenes do?
stimulate cell division / mitosis
